1. Field of the Invention
The present invention relates to a method of allocating vocoder resources in a mobile communication system using a code division multiaccess (CDMA) system, and more particularly during a simultaneous transfer of voice and data in a mobile communication system.
2. Discussion of Related Art
A mobile communication (MC) system using a CDMA system generally includes a plurality of mobile stations, each mobile station corresponding to one of a plurality of base stations; and a plurality of base station controllers connected to a mobile switching center (MSC). The MC system allows a bidirectional transmission of voice and data among the plurality of mobile stations. Specifically, the MC system provides a transmission rate of approximately 8 kbps between a mobile station and the corresponding base station by a dynamic variable data speed (DVDS) vocoder algorithm.
The DVDS vocoder algorithm is implemented by the operation of selector/vocoder cards (SVC) within the base station controllers. A single SVC consists of one selector and eight vocoders. During the transmission of voice, each vocoder codes the voice frame into voice packets, and decodes the transmitted voice packet into voice sampling data.
The vocoders provide a four-step (9600 bps, 4800 bps, 2400 bps, and 1200 bps) bit frame transmission speeds. The specific transmission speed depends on several factors, one of which is the volume of data to be received/transmitted. However, the transmission speed is mainly dependent upon an input variable raue.
The vocoder employs an adjustable threshold to determine the input variable rate. Basically, the threshold is adjusted according to the level of background noise, but upon receipt of voice data, the threshold is substantially raised. Therefore, the speed of a vocoder, and thus the transmission rate between a mobile and a base station, is generally selected according to an adjustable threshold. By taking into consideration the background noise level, the MC system provides a high quality communication service.
Nonetheless, an advanced communication system must be capable of simultaneously transmitting multimedia such as voice and data such as fax, video, and text. However, a simultaneous transfer of voice and data requires a high number of vocoder resources. Thus, during such transmittal, the availability of the vocoder resources in the base station controller may significantly decrease.
Particularly, if a mobile station requests a simultaneous voice and data transfer service, the corresponding base station informs the base station controller of the receipt of a radio signal containing voice and data frame. The base station controller receives the voice and data frame from the base station, and transmits the data to the MSC. Thus, the frame transmitted to the MSC contains both voice data and non-voice data.
The voice frame must be transmitted to the vocoder in real time by a pulse code modulation (PCM) frame of 64 kbps. An allocated vocoder receives the digitized voice frame and codes the frame into voice packets. However, a separate vocoder must be allocated to the non-voice frame because non-voice frame already comes in packets. Specifically, the non-voice frame bypasses the PCM and merely passes through a vocoder without any coding. As a result, a single vocoder cannot be allocated to transmit both the voice and non-voice data.
Therefore, when a mobile station requests a simultaneous voice and data transfer service, a corresponding base station controller must allocate two vocoder resources in order to effectively perform the voice and data transfer service. Accordingly, when a plurality of mobile stations request the simultaneous transfer service, the availability of vocoder resources can significantly decrease. For example, if four mobile stations request a simultaneous transfer of voice and data, the base station controller must allocate eight vocoders.
Therefore, in the related art, a multiple number of simultaneous transfer of voice and data could not be accomplished without increasing the number of vocoders. Consequently, allocating separate vocoders to simultaneously transfer voice and data is inefficient and unsuitable for the multimedia communication.
Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the related art.
Another object of the present invention is to provide a method of allocating vocoder resources in a CDMA mobile communication system.
A further object of the present invention is to provide a method of allocating vocoder resources in a CDMA mobile communication system during a simultaneous transfer of voice and data.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purposes of the invention, as embodied and broadly described herein, one embodiment of the present invention discloses a method of allocating a set of vocoders for processing a voice frame and extra vocoders for processing at least one data frame varied at a given frame rate.
According to another embodiment, the present invention discloses a method of allocating vocoder resources for processing data frame while the base station is already processing voice frame by conducting service negotiations between the mobile station and the corresponding SVC before allocating a vocoder for processing a voice frame and extra vocoders for varying the rate of a plurality of data frames.